Seedless particles with carbon allotropes

ABSTRACT

Carbon materials having carbon aggregates, where the aggregates include carbon nanoparticles and no seed particles, are disclosed. In various embodiments, the nanoparticles include graphene, optionally with multi-walled spherical fullerenes and/or another carbon allotrope. In various embodiments, the nanoparticles and aggregates have different combinations of: a Raman spectrum with a 2D-mode peak and a G-mode peak, and a 2D/G intensity ratio greater than 0.5, a low concentration of elemental impurities, a high Brunauer-Emmett and Teller (BET) surface area, a large particle size, and/or a high electrical conductivity. Methods are provided to produce the carbon materials.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/676,649, filed on Aug. 14, 2017 and entitled “MicrowaveChemical Processing Reactor”; which is a continuation of U.S. patentapplication Ser. No. 15/428,474, filed on Feb. 9, 2017, entitled“Microwave Chemical Processing Reactor” and issued as U.S. Pat. No.9,767,992; all of which are hereby incorporated by reference in theirentirety.

BACKGROUND

Carbon particles containing graphite and graphene are used in a widerange of applications ranging from car tire additives, to lubricants, toelectronic materials. Some properties that enable their use in such awide array of applications are high surface areas, and high electricaland thermal conductivities.

Naturally occurring graphene and graphite materials are mined andprocessed for use in different applications. Naturally occurringgraphite and graphene materials contain high concentrations ofimpurities, and it is difficult and costly to purify naturally occurringgraphite and graphene to obtain higher purity materials.

Various crude or refined hydrocarbons (e.g., methane, ethane, propane,etc.) can also be pyrolized or cracked to produce higher-order carbonsubstances such as graphene and fullerenes, and hydrogen. However, someof the processes used to produce higher-order carbon substances requirethe use of catalysts, such as metal catalysts, and result in thepresence of impurities within the higher-order carbon substances.Furthermore, some processes require the formation of a “seed” or “core”around which the higher-order carbon substances are formed.Additionally, some of these pyrolysis or cracking processes produceparticles that are very small (e.g., less than 100 nm in diameter) andare difficult and expensive to collect.

Some examples of higher-order carbon allotropes are shown in FIGS.1A-1D. FIG. 1A shows a schematic of graphite, where carbon formsmultiple layers of a two-dimensional, atomic-scale, hexagonal lattice inwhich one atom forms each vertex. Graphite is made of single layers ofgraphene. FIG. 1B shows a schematic of a carbon nanotube, where carbonatoms form a hexagonal lattice that is curved into a cylinder. Carbonnanotubes can also be referred to as cylindrical fullerenes. FIG. 1Cshows a schematic of a C60 buckminsterfullerene, where a single layer ofa hexagonal lattice of carbon atoms forms a sphere. Other sphericalfullerenes exist that contain single layers of hexagonal lattices ofcarbon atoms, and can contain 60 atoms, 70 atoms, or more than 70 atoms.FIG. 1D shows a schematic of a carbon nano-onion from U.S. Pat. No.6,599,492, which contains multiple concentric layers of sphericalfullerenes.

SUMMARY

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including graphene, with no seedparticles. The graphene in the carbon material has up to 15 layers. Aratio of carbon to other elements, except hydrogen, in the carbonaggregates is greater than 99%. A median size of the carbon aggregatesis from 1 to 50 microns. A surface area of the carbon aggregates is atleast 50 m²/g, when measured using a Brunauer-Emmett-Teller (BET) methodwith nitrogen as the adsorbate. The carbon aggregates, when compressed,have an electrical conductivity greater than 500 S/m.

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including graphene andmulti-walled spherical fullerenes, with no seed particles. The graphenein the carbon material has up to 15 layers. A Raman spectrum of thecarbon material comprising the multi-walled spherical fullerenes, using532 nm incident light, has: a D-mode peak, a G-mode peak, and a D/Gintensity ratio less than 1.2. A ratio of carbon to other elements,except hydrogen, in the carbon aggregates is greater than 99%. A mediansize of the carbon aggregates is from 1 to 100 microns. A surface areaof the carbon aggregates is at least 10 m²/g, when measured using a BETmethod with nitrogen as the adsorbate. The carbon aggregates, whencompressed, have an electrical conductivity greater than 500 S/m.

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including a mixture of grapheneand at least one other carbon allotrope, with no seed particles. Thegraphene in the carbon material has up to 15 layers. A ratio of carbonto other elements, except hydrogen, in the carbon aggregates is greaterthan 99%. A median size of the carbon aggregates is from 1 to 100microns. A surface area of the carbon aggregates is at least 10 m²/g,when measured using a BET method with nitrogen as the adsorbate. Thecarbon aggregates, when compressed, have an electrical conductivitygreater than 100 S/m.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are schematics of carbon allotropes from the prior art.

FIG. 1E is a schematic of idealized connected multi-walled sphericalfullerenes, in accordance with some embodiments.

FIG. 2A is a simplified vertical cross-section of a microwave gasprocessing system, in accordance with some embodiments of the presentdisclosure.

FIG. 2B is a simplified vertical cross-section of a microwave gasprocessing system having a filament, in accordance with embodiments ofthe present disclosure.

FIG. 3 is a flowchart of methods for generating the carbon particles,nanoparticles, aggregates and materials in accordance with embodimentsof the present disclosure

FIG. 4A shows a Raman spectrum from as-synthesized carbon aggregatescontaining graphite and graphene in a first example, in accordance withsome embodiments.

FIGS. 4B and 4C show scanning electron microscope (SEM) images fromas-synthesized carbon aggregates containing graphite and graphene in afirst example, in accordance with some embodiments.

FIGS. 4D and 4E show transmission electron microscope (TEM) images fromas-synthesized carbon aggregates containing graphite and graphene in afirst example, in accordance with some embodiments.

FIG. 5A shows a top down image of as-synthesized carbon aggregatescontaining graphite, graphene and multi-walled spherical fullerenes in asecond example, in accordance with some embodiments.

FIG. 5B shows a Raman spectrum from locations shown in FIG. 5A ofas-synthesized carbon aggregates containing multi-walled sphericalfullerenes in a second example, in accordance with some embodiments.

FIG. 5C is the top down image of FIG. 5A with different locationshighlighted.

FIG. 5D shows a Raman spectrum from locations shown in FIG. 5C ofas-synthesized carbon aggregates containing graphite and graphene in asecond example, in accordance with some embodiments.

FIGS. 5E-5J show TEM images from as-synthesized carbon aggregatescontaining graphite, graphene and multi-walled spherical fullerenes in asecond example, in accordance with some embodiments.

FIGS. 6A and 6B show Raman spectra from as-synthesized carbon aggregatescontaining graphite, graphene and amorphous carbon in a third example,in accordance with some embodiments.

FIGS. 6C-6E show TEM images from as-synthesized carbon aggregatescontaining graphite, graphene and amorphous carbon in a third example,in accordance with some embodiments.

DETAILED DESCRIPTION

The present disclosure relates to carbon nanoparticles and aggregatesthat include different allotropes of (i.e., various forms of) carbon,including graphite, graphene, fullerenes, amorphous carbon andcombinations thereof, as described below. In some embodiments, thecarbon nanoparticles and aggregates are characterized by a high degreeof order (i.e., low concentration of defects), and/or high purity (i.e.,low concentration of elemental impurities), in contrast to the lessordered and lower purity particles achievable with conventional systemsand methods.

The form-factors of the materials described herein are particles (e.g.,nanoparticles or aggregates). The form-factors are not films, which arearranged on objects or substrates. In some embodiments, the carbonparticles described herein are core-less or seedless (i.e., do notcontain a core or a seed of a material other than carbon). In someembodiments, the carbon aggregates described herein are characterized bya size that is substantially larger than comparable prior art particles.

Conventional methods have been used to produce particles containinggraphite and graphene with a high degree of order, but the conventionalmethods lead to carbon products with a variety of shortcomings. Forexample, naturally occurring graphite can be chemically processed toproduce graphene with high electrical conductivities and high surfaceareas, but the purity is low. In some cases, the particles can bechemically purified to some degree; however, the processes to do so aredifficult and costly. In some cases, conventional purification processesproduce particles with appreciable concentrations of oxygen, which canreduce the electrical conductivity of the material. Hydrocarbonpyrolysis and cracking methods have also been used to produce particlescontaining graphite and graphene with a high degree of order (e.g., asevidenced by Raman signatures of ordered material); however, theparticles have low purity (e.g., less than 95% carbon to otherelements). In some cases hydrocarbon pyrolysis and cracking methodsutilizing catalysts or seed particles lead to products that include thecatalyst or seed elements and therefore have low purity (e.g., less than95% carbon to other elements). In some cases, pyrolysis and crackingmethods also produce particles with small particle sizes (e.g., lessthan 100 nm), which makes the particles difficult and expensive tocollect. The undesirable properties of the carbon allotropes producedusing conventional methods, such as a low degree of order and/or lowpurity, often lead to undesirable electrical properties of the resultingcarbon particles (e.g., low electrical conductivity, or low surfacearea).

In some cases, conventional methods are capable of producing particlescontaining carbon allotropes with one or more desirable properties, butlack a desirable combination of properties. For example, someconventional methods are capable of producing graphene with high surfacearea, but low electrical conductivity due to the presence of residualoxygen.

The seedless carbon nanoparticles and aggregates described herein havelow concentration of elemental impurities, and have large particlessizes, high surface areas and high electrical conductivitiesas-synthesized. In some embodiments, the carbon nanoparticles andaggregates described herein are produced using relatively high speed,low cost, improved microwave reactors and methods, as described below.Additional advantages and/or improvements will also become apparent fromthe following disclosure.

In the present disclosure, the term “graphene” refers to an allotrope ofcarbon in the form of a two-dimensional, atomic-scale, hexagonal latticein which one atom forms each vertex. The carbon atoms in graphene aresp²-bonded. Additionally, graphene has a Raman spectrum with three mainpeaks: a G-mode at approximately 1580 cm⁻¹, a D-mode at approximately1350 cm⁻¹, and a 2D-mode peak at approximately 2690 cm⁻¹ (when using a532 nm excitation laser). In the present disclosure, a single layer ofgraphene is a single sheet of hexagonally arranged (i.e., sp²-bonded)carbon atoms. It is known that the ratio of the intensity of the 2D-modepeak to the G-mode peak (i.e., the 2D/G intensity ratio) is related tothe number of layers in the graphene. A higher 2D/G intensity ratiocorresponds to fewer layers in multilayer graphene materials. Indifferent embodiments of the present disclosure, graphene contains fewerthan 15 layers of carbon atoms, or fewer than 10 layers of carbon atoms,or fewer than 7 layers of carbon atoms, or fewer than 5 layers of carbonatoms, or fewer than 3 layers of carbon atoms, or contains a singlelayer of carbon atoms, or contains from 1 to 10 layers of carbon atoms,or contains from 1 to 7 layers of carbon atoms, or contains from 1 to 5layers of carbon atoms. In some embodiments, few layer graphene (FLG)contains from 2 to 7 layers of carbon atoms. In some embodiments, manylayer graphene (MLG) contains from 7 to 15 layers of carbon atoms.

In the present disclosure, the term “graphite” refers to an allotrope ofcarbon in the form of a two-dimensional, atomic-scale, hexagonal latticein which one atom forms each vertex. The carbon atoms in graphite aresp²-bonded. Additionally, graphite has a Raman spectrum with two mainpeaks: a G-mode at approximately 1580 cm⁻¹ and a D-mode at approximately1350 cm⁻¹ (when using a 532 nm excitation laser). Similar to graphene,graphite contains layers of hexagonally arranged (i.e., sp²-bonded)carbon atoms. In different embodiments of the present disclosure,graphite can contain greater than 15 layers of carbon atoms, or greaterthan 10 layers of carbon atoms, or greater than 7 layers of carbonatoms, or greater than 5 layers of carbon atoms, or greater than 3layers of carbon atoms.

In the present disclosure, the term “fullerene” refers to a molecule ofcarbon in the form of a hollow sphere, ellipsoid, tube, or other shapes.Spherical fullerenes can also be referred to as Buckminsterfullerenes,or buckyballs. Cylindrical fullerenes can also be referred to as carbonnanotubes. Fullerenes are similar in structure to graphite, which iscomposed of stacked graphene sheets of linked hexagonal rings.Fullerenes may also contain pentagonal (or sometimes heptagonal) rings.

In the present disclosure, the term “multi-walled fullerene” refers tofullerenes with multiple concentric layers. For example, multi-wallednanotubes (MWNTs) contain multiple rolled layers (concentric tubes) ofgraphene. Multi-walled spherical fullerenes (MWSFs) contain multipleconcentric spheres of fullerenes.

In the present disclosure, the term “amorphous carbon” refers to acarbon allotrope that has minimal or no crystalline structure. Onemethod for characterizing amorphous carbon is through the ratio of sp²to sp³ hybridized bonds present in the material. The sp² to sp³ ratioscan be determined by comparing the relative intensities of variousspectroscopic peaks (including EELS, XPS, and Raman spectroscopy) tothose expected for carbon allotropes with sp² or sp³ hybridization.

In the present disclosure, the term “nanoparticle” refers to a particlethat has a size from 1 nm to 900 nm. The nanoparticle can include one ormore type of structure (e.g., crystal structure, defect concentration,etc.), and one or more type of atom. The nanoparticle can be any shape,including but not limited to spherical shapes, spheroidal shapes,dumbbell shapes, cylindrical shapes, elongated cylindrical type shapes,rectangular prism shapes, disk shapes, wire shapes, irregular shapes,dense shapes (i.e., with few voids), porous shapes (i.e., with manyvoids), etc. In the present disclosure, the term “particle” refers to aparticle that has any size, including nanoparticles.

In the present disclosure, the term “aggregate” refers to a plurality ofparticles or nanoparticles that are connected together by Van der Waalsforces, by covalent bonds, by ionic bonds, by metallic bonds, or byother physical or chemical interactions. Aggregates can vary in sizeconsiderably, but in general are larger than about 500 nm. Throughoutthis application, the terms “particle” or “particles” are generic termsthat can include any size particles, including nanoparticles andaggregates.

The carbon particles and nanoparticles described herein contain graphiteand graphene, with no seed particles. In some embodiments, the particlesand nanoparticles described herein contain graphite containing greaterthan 15 layers of carbon atoms, or greater than 10 layers of carbonatoms, or greater than 7 layers of carbon atoms, or greater than 5layers of carbon atoms, or greater than 3 layers of carbon atoms, andgraphene containing fewer than 15 layers of carbon atoms, or fewer than10 layers of carbon atoms, or fewer than 7 layers of carbon atoms, orfewer than 5 layers of carbon atoms, or fewer than 3 layers of carbonatoms, or contain a single layer of carbon atoms, or contain from 1 to10 layers of carbon atoms, or contain from 1 to 7 layers of carbonatoms, or contain from 1 to 5 layers of carbon atoms, with no seedparticles. In some embodiments, a plurality of the carbon particles ornanoparticles are contained within a carbon aggregate. In someembodiments, a carbon material contains a plurality of the carbonaggregates.

In some embodiments, the carbon particles or nanoparticles furthercomprise multi-walled spherical fullerenes (MWSFs). In some embodiments,the carbon particles or nanoparticles further comprise connected MWSFs,with layers of graphene coating the connected MWSFs. In someembodiments, the carbon particles or nanoparticles further compriseamorphous carbon.

In some embodiments, the particles and aggregates described hereincontain a mixture of graphene and a second allotrope of carbon, and donot contain a seed particle. In some embodiments, the second allotropeof carbon is graphite, MWSFs, connected MWSFs, or amorphous carbon. Insome embodiments, the particles and aggregates contain a mixture ofgraphene, a second allotrope of carbon, and a third allotrope of carbon,and do not contain a seed particle. In some embodiments, the secondallotrope is graphite and the third allotrope is MWSFs, connected MWSFs,or amorphous carbon.

In some embodiments, the carbon nanoparticles and aggregates describedherein are characterized by a well-ordered structure with high purity asillustrated by an idealized carbon nanoparticle 100 shown in FIG. 1E.The carbon allotrope in FIG. 1E contains two connected multi-walledspherical fullerenes (MWSFs) 101 and 102 with layers of graphene 103coating the connected MWSFs 101 and 102. The allotrope shown in FIG. 1Eis also core-less (i.e., does not contain a core of a material otherthan carbon at the center of the spherical fullerene). The idealizednanoparticle shown in FIG. 1E has high uniformity since the ratio ofMWSFs to graphene is high, is well-ordered since there are no pointdefects (e.g., missing carbon atoms) and no distorted carbon lattices,and has a high purity since there are no elements (e.g., a core ofimpurities) other than carbon, in contrast with low uniformity mixturesof MWSFs mixed with other carbon allotropes, poorly-ordered MWSFs withmany point defects and distorted lattices, and low purity MWSFs (e.g.,with seed particles at the core). In other embodiments, the connectedMWSFs do contain a core. In some embodiments, the core is a void, or acarbon-based material that is not an MWSF (e.g., amorphous carbon), or aseed that is not carbon-based.

In some embodiments, the aggregates described herein contain graphene(e.g., containing up to 15 layers) and graphite (e.g., containinggreater than 15 layers) and have a ratio of graphene to graphite from20% to 80%, a high degree of order (e.g., a Raman signature with theratio of the intensity of the 2D-mode peak to the G-mode peak greaterthan 0.5), and a high purity (e.g., the ratio of carbon to otherelements, other than H, is greater than 99.9%). In some embodiments, theratio graphene to graphite is from 10% to 90%, or from 10% to 80% orfrom 10% to 60%, or from 10% to 40%, or from 10% to 20%, or from 20% to40%, or from 20% to 90%, or from 40% to 90%, or from 60% to 90%, or from80% to 90%. In some embodiments, the particles produced using themethods described herein contain graphite and graphene, and do notcontain a core composed of impurity elements other than carbon. In somecases, the aggregates of the particles have large diameters (e.g.,greater than 10 microns across).

In some embodiments, the aggregates described herein contain graphene,MWSFs or connected MWSFs, and optionally graphite, and have a ratio ofgraphene to MWSF from 20% to 80%, a high degree of order (e.g., a Ramansignature with ratio of the intensities of the D-mode peak to G-modepeak from 0.95 to 1.05), and a high purity (e.g., the ratio of carbon toother elements, other than H, is greater than 99.9%). In someembodiments, the ratio graphene to MWSFs or connected MWSFs is from 10%to 90%, or from 10% to 80% or from 10% to 60%, or from 10% to 40%, orfrom 10% to 20%, or from 20% to 40%, or from 20% to 90%, or from 40% to90%, or from 60% to 90%, or from 80% to 90%. In some embodiments, theparticles produced using the methods described herein contain MWSFs orconnected MWSFs, and the MWSFs do not contain a core composed ofimpurity elements other than carbon. In some cases, the aggregates ofthe particles have large diameters (e.g., greater than 10 micronsacross).

In some embodiments, the aggregates described herein contain graphene,amorphous carbon, and optionally graphite, and have a ratio of grapheneto amorphous carbon from 20% to 80%, and have a high purity (e.g., theratio of carbon to other elements, other than H, is greater than 99.9%).In some embodiments, the ratio graphene to amorphous carbon is from 10%to 90%, or from 10% to 80% or from 10% to 60%, or from 10% to 40%, orfrom 10% to 20%, or from 20% to 40%, or from 20% to 90%, or from 40% to90%, or from 60% to 90%, or from 80% to 90%. In some embodiments, theparticles produced using the methods described herein contain amorphouscarbon, and do not contain a core composed of impurity elements otherthan carbon. In some cases, the aggregates of the particles have largediameters (e.g., greater than 10 microns across).

In some embodiments, the carbon material has a ratio of carbon to otherelements, except Hydrogen, greater than 99%, or greater than 99.5%, orgreater than 99.7%, or greater than 99.9%, or greater than 99.95%.

In some embodiments, the median size of the carbon aggregates is from 1micron to 50 microns, or from 2 microns to 20 microns, or from 5 micronsto 40 microns, or from 5 microns to 30 microns, or from 10 microns to 30microns, or from 10 microns to 25 microns, or from 10 microns to 20microns. In some embodiments, the size distribution of the carbonaggregates has a 10^(th) percentile from 1 micron to 10 microns, or from1 micron to 5 microns, or from 2 microns to 6 microns, or from 2 micronsto 5 microns. The size of the particles that make up the aggregates canvary in size, and can be smaller than 10 nm or up to hundreds ofnanometers in size. In some embodiments, the size of aggregates ismeasured using TEM images. In some embodiments, the size of theaggregates is measured using a laser particle size analyzer (e.g., aFritsch Analysette 22 MicroTec plus).

In some embodiments, the surface area of the carbon aggregates, whenmeasured using the Brunauer-Emmett-Teller (BET) method with nitrogen asthe adsorbate (i.e., the “BET method using nitrogen”, or the “nitrogenBET method”) or the Density Functional Theory (DFT) method, is from 50to 300 m²/g, or from 100 to 300 m²/g, or from 50 to 200 m²/g, or from 50to 150 m²/g, or from 60 to 110 m²/g, or from 50 to 100 m²/g, or from 70to 100 m²/g.

In some embodiments, the carbon aggregates, when compressed (e.g., intoa disk, pellet, etc.), and optionally annealed, have an electricalconductivity greater than 500 S/m, or greater than 1000 S/m, or greaterthan 2000 S/m, or from 500 S/m to 20,000 S/m, or from 500 S/m to 10,000S/m, or from 500 S/m to 5000 S/m, or from 500 S/m to 4000 S/m, or from500 S/m to 3000 S/m, or from 2000 S/m to 5000 S/m, or from 2000 S/m to4000 S/m, or from 1000 S/m to 5000 S/m, or from 1000 S/m to 3000 S/m.

The carbon nanoparticles and aggregates described herein arecharacterized by Raman spectroscopy to determine the species of carbonallotropes present, and their degree of order. The main peaks in theRaman spectra for graphite and graphene are the G-mode, the D-mode andthe 2D-mode. The G-mode peak has a wave number of approximately 1580cm⁻¹, and is attributed to the vibration of carbon atoms insp²-hybridized carbon networks. The D-mode peak has a wave number ofapproximately 1350 cm⁻¹, and can be related to the breathing ofhexagonal carbon rings with defects. The 2D-mode peak is a second-orderovertone of the D-mode and has a wave number of approximately 2690 cm⁻¹.

In some embodiments, the graphite- and graphene-containing carbonmaterials have a Raman spectrum (using 532 nm incident light) with a2D-mode peak and a G-mode peak, and the 2D/G intensity ratio is greaterthan 0.2, or greater than 0.5, or greater than 1.

Raman spectroscopy can also be used to characterize the structure ofMWSFs. When using 532 nm incident light, the Raman G-mode is typicallyat 1582 cm⁻¹ for planar graphite, but can be downshifted for MWSFs(e.g., to 1565-1580 cm⁻¹). The D-mode is observed at approximately 1350cm⁻¹ in the Raman spectra of MWSFs. The ratio of the intensities of theD-mode peak to G-mode peak (i.e., the D/G intensity ratio) is related tothe degree of order of the MWSFs, where a lower D/G intensity ratioindicates higher degree of order. A D/G intensity ratio near or below 1indicates a relatively high degree of order, and a D/G intensity ratiogreater than or equal to 1.2 indicates lower degree of order.

In some embodiments, the carbon materials containing the MWSFs have aRaman spectrum (using 532 nm incident light) with a D-mode peak and aG-mode peak, and the D/G intensity ratio is from 0.9 to 1.1, or lessthan about 1.2.

In some embodiments, the carbon materials containing amorphous carbonhave a Raman spectrum (using 532 nm incident light) with a 2D-mode peak,a D-mode peak and a G-mode peak, and the D/G intensity ratio is greaterthan 0.5. In some embodiments, the Raman spectrum also has a lowintensity 2D-mode peak. In some embodiments, the 2D-mode peak has anintensity less than approximately 30% of the G-mode peak intensity, orless than 20% of the G-mode peak intensity, or less than 10% of theG-mode peak intensity. In some embodiments, the Raman spectrum has aD-mode peak and G-mode peak with a shallow valley between them. In someembodiments, the minimum intensity of the shallow valley between theD-mode peak and the G-mode peak is greater than approximately 40% of theG-mode peak intensity, or greater than approximately 50% of the G-modepeak intensity, or greater than approximately 60% of the G-mode peakintensity.

Methods for Proucing Graphite and Graphene Materials E

In some embodiments, the carbon particles, nanoparticles, aggregates andmaterials described herein are produced using microwave plasma reactorsand methods, such as any appropriate microwave reactor and/or methoddescribed in U.S. patent application Ser. No. 15/351,858, entitled“Microwave Chemical Processing,” or in the aforementioned U.S. patentapplication Ser. No. 15/428,474, entitled “Microwave Chemical ProcessingReactor,” which are assigned to the same assignee as the presentapplication, and are incorporated herein by reference as if fully setforth herein for all purposes. Additional information and embodimentsfor microwave plasma gas processing system methods and apparatuses toproduce the carbon nanoparticles and aggregates described herein arealso described in the aforementioned U.S. Patent Applications.

In some embodiments, microwave plasma chemical processing of processmaterials (e.g., hydrocarbon gases, or liquid mixtures) is used toproduce the carbon particles, nanoparticles and aggregates describedherein. More specifically, microwave plasma chemical processing ofprecursor materials using various techniques, including pulsing of themicrowave radiation to control the energy of the plasma, can be used toproduce the carbon nanoparticles and aggregates described herein. Theability to control the energy of the plasma enables the selection of oneor more reaction pathways in conversion of the precursor materials intospecific separated components. Pulsed microwave radiation can be used tocontrol the energy of the plasma, because the short-lived high-energyspecies that are created when a plasma ignites can be re-generated atthe start of each new pulse. The plasma energy is controlled to have alower average ion energy than conventional techniques, but at a highenough level to enable the targeted chemical reactions to occur at highprecursor material flows and high pressures.

Conventional microwave plasma chemical processing systems using pulsedmicrowave radiation to control the energy of the plasma have very highcracking efficiency, in excess of 90%. These conventional systems,however, use low gas flow rates, below 1 standard liter per minute(slm), and small gas volumes within the plasma, with a consequence thatthe production rate is low and the production cost is high. Theseconventional systems cannot increase the gas flow rate and the gasvolume within the plasma while using high frequency microwave pulsing(e.g., above approximately 100 Hz) because the plasma cannot ignite fastenough to keep up with the pulses when a large volume and high flow ofgas is used.

In contrast to previously developed systems, in some embodiments, amicrowave plasma can be generated in a supply gas and/or precursormaterial, and the energy in the plasma is sufficient to form separatedcomponents, including the carbon nanoparticles and aggregates describedherein, from precursor material molecules. In some embodiments, a sourceof microwave radiation is coupled to a reaction chamber, the plasma isgenerated along a first portion of the length of the reaction chamber,and the precursor material is separated into components, including thecarbon nanoparticles and aggregates described herein, along a secondportion of the length of the reaction chamber. In some embodiments, themicrowave radiation is coupled directly into the plasma and not througha dielectric wall as in conventional methods.

In methods of the present embodiments regarding microwave plasmachemical processing of precursor materials to produce the carbonnanoparticles and aggregates described herein, pulsed microwaveradiation is supplied through a waveguide having a length, where themicrowave radiation propagates in a direction along the waveguide. Apressure within the waveguide is at least 0.1 atmosphere. A supply gasis provided into the waveguide at a first location along a length of thewaveguide, where a majority of the supply gas flows in the direction ofthe microwave radiation propagation. A plasma is generated in the supplygas in at least a portion of the length of the waveguide, and aprecursor material (e.g., a process gas, or a liquid precursor) is addedinto the waveguide at a second location downstream from the firstlocation. A majority of the precursor material flows in the direction ofthe microwave propagation at a rate greater than 5 slm, or greater than5 L/min for liquid mixtures. An average energy of the plasma iscontrolled to convert the precursor material into separated components,including the carbon nanoparticles and aggregates described herein, bycontrolling at least one of i) a pulsing frequency of the pulsedmicrowave radiation, where the pulsing frequency is greater than 500 Hz;and ii) a duty cycle of the pulsed microwave radiation, where the dutycycle is less than 90%.

In gas processing systems of the present embodiments regarding microwaveplasma chemical processing of precursor materials to produce the carbonnanoparticles and aggregates described herein, the systems include awaveguide having a first gas inlet, a second gas inlet downstream of thefirst gas inlet, and a length. The first inlet is configured to receivea supply gas, and the second inlet is configured to receive a precursormaterials (e.g., a process gas, or a liquid mixture). A pulsed microwaveradiation source is coupled to the waveguide to generate a plasma in thesupply gas, where the microwave radiation propagates in a directionalong the length of the waveguide to react with the precursor material.The microwave radiation source is configured to pulse microwaveradiation on and off at a frequency from 500 Hz to 1000 kHz and with aduty cycle less than 90%. The majority of the flow of the supply gas andthe majority of the flow of the precursor material are parallel to thedirection of the microwave propagation. The flow of the process gas isgreater than 5 slm, and the waveguide is configured to accommodatepressures of at least 0.1 atmosphere.

FIG. 2A shows an embodiment of a microwave chemical processing system ofthe present disclosure, in which a “field-enhancing waveguide” (FEWG) iscoupled to a microwave energy generator (i.e., a microwave energysource), a plasma is generated from a supply gas in a plasma zone of theFEWG, and a reaction length of the FEWG serves as the reaction zone toseparate the process material into separate components. The presentreactor as demonstrated by FIG. 2A is absent of a dielectric barrierbetween the field-enhancing zone of the field-enhancing waveguide andthe reaction zone. In contrast, the reaction zones of conventionalsystems, are enclosed within a dielectric barrier such as a quartzchamber as explained previously. The direction of propagation of themicrowave energy is parallel to the majority of the flow of the supplygas and/or the process material (i.e., precursor material), and themicrowave energy enters the waveguide upstream of the portion of theFEWG where the separated components are generated.

As shown in FIG. 2A, a microwave chemical processing reactor 200, inaccordance with some embodiments, generally includes a FEWG 205, one ormore inlets 202 configured to receive supply gas and/or process material208 a flowing into the FEWG 205, and a microwave energy source 204 thatis coupled to the FEWG 205, among other elements not shown forsimplicity. The “process material” can also be referred to as a“precursor material”, or in some embodiments, a “process gas”. Theinlets 202 can be designed to accommodate gaseous or liquid mixtureprecursor materials. In the case of liquid precursors, in someembodiments, the inlet 202 can include an atomizer (or other assembly)to effectively disperse the liquid precursor in the reactor. In someembodiments, a bubbler can be used to vaporize a liquid, and the vaporprovided to the inlet 202.

In some embodiments, microwave circuit 207 controls a pulsing frequencyat which microwave energy 209 from microwave energy source 204 ispulsed. In some embodiments, the microwave energy 209 from microwaveenergy source 204 is continuous wave.

The FEWG 205 has a length L. The portion of the FEWG 205 with lengthL_(A) (shown in FIG. 2A) is closer to the microwave energy generatorthan the portion of the FEWG with length L_(B) (shown in FIG. 2A).Throughout this disclosure, different portions of the FEWG will bedescribed by a capital L with a subscript denoting the certain portionof the FEWG (e.g., L_(A), L₀, L_(B), L₁ , L₂), and synonymously, thelengths of the different portions of the FEWG will also be described bya capital L with a subscript denoting the length of a certain portion ofthe FEWG (e.g., L_(A), L₀, L_(B), L₁, L₂).

The cross-sectional area of the FEWG in length L_(B) is smaller than thecross-sectional area of the FEWG in length L_(A). The length of the FEWGL₀, is located between lengths L_(A) and L_(B) of the FEWG, and has adecreasing cross-sectional area along the path of the microwave energypropagation. The decrease in cross-sectional area serves to concentratethe electric field, thus increasing the microwave energy density whilestill providing a significant amount of area in which plasma can beformed compared to conventional systems. The portion of the FEWG withlength L_(B) (shown in FIG. 2A) may have a rectangular cross-section ofdimensions 0.75 inches by 3.4 inches when using a microwave energyfrequency of 2.45 GHz. This cross-sectional area is much greater thanconventional systems where the plasma generation area is generally lessthan one square inch. The dimensions of the different portions of theFEWG 205 are set according to the microwave frequency, in order toproperly function as a waveguide. For example, for an ellipticalwaveguide the cross-sectional dimensions can be 5.02 inches by 2.83inches for 2.1-2.7 GHz.

In conventional microwave plasma materials processing systems, thelimited region in which plasma can form, such as less than one squareinch as described above, constrains the volume in which gas reactionscan occur. Also, in conventional systems the microwave energy enters thereaction chamber through a window (typically quartz). In these systems,dielectric materials (e.g., particulate carbon) are coated on the windowduring processing leading to a decreased power delivery over time. Thiscan be highly problematic if these separated components absorb microwaveenergy because they can prevent the microwave energy from coupling intothe reaction chamber to generate the plasma. Consequently, a rapidbuild-up of by-products, such as carbon particles that are produced fromthe gas reactions, occurs and limits the run-time of the processingequipment. In the present embodiments, the system 200 and otherembodiments described below are designed without the use of a window inthe reaction zone; that is, using a parallel propagation/gas flow systemwhere the energy enters upstream from the reaction. As a result, moreenergy and power can be coupled into the plasma from the microwaveenergy source. The lack of a window and the greater volume within thewaveguide 205, compared to limited reaction chamber volumes inconventional systems, greatly reduces the issue of particle build-upcausing limited run-times, thus improving production efficiency of themicrowave processing system.

The microwave energy 209 in FIG. 2A creates a microwave plasma 206 inthe supply gas and/or process material within a plasma zone with lengthL₁ (shown in FIG. 2A) of the length of the FEWG 205. The plasma zonewith length L₁ is located within the portion of the FEWG L_(B), wherethe cross-sectional area is smaller and the microwave energy density ishigher than in length L_(A). In some embodiments, a supply gas that isdifferent from the process material is used to generate the microwaveplasma 206. The supply gas may be, for example, hydrogen, helium,nitrogen, a noble gas such as argon, or mixtures of more than one typeof gas. In other embodiments, the supply gas is the same as the processmaterial, where the process material is the material from whichseparated components are being created.

In some embodiments, the supply gas and/or process material inlet 202 islocated upstream from the portion of the FEWG L_(B), or is locatedwithin the portion of the FEWG L₀, or is located within the portion ofthe FEWG L_(A), or is located upstream of the portion of the FEWG L_(A).In some embodiments, the portion of the FEWG L₁extends from a positionalong the FEWG downstream from the position where the supply gas and/orprocess material 208 a enters the FEWG, to the end of the FEWG or to aposition between the entrance of the supply gas and/or process materialand the end of the FEWG 205. In some embodiments, the portion of theFEWG L₁ extends from where the supply gas and/or process material 208 aenters the FEWG, to the end of the FEWG or to a position between theentrance of the supply gas and/or process material and the end of theFEWG.

The generated plasma 206 provides energy for reactions to occur inprocess material 208 b within a reaction zone 201 of the FEWG 205 havinga reaction length L₂. In some embodiments, reaction zone L₂ extends fromwhere the process material 208 a enters the FEWG 205, to the end of theFEWG 205 or to a position between the entrance of the process materialand the end of the FEWG 205. Given the right conditions, the energy inthe plasma 206 will be sufficient to form separated components from theprocess material molecules. One or more outlets 203 are configured tocollect the separated products out of the FEWG 205 downstream of thereaction zone portion 201 of the FEWG where reactions occur in theprocess material 208 b. In the example shown in FIG. 2A, the propagationdirection of the microwave energy 209 is parallel with the majority ofthe supply gas and/or process material flow 208 b, and the microwaveenergy 209 enters the FEWG 205 upstream of the reaction zone 201 of theFEWG where the separated components are generated.

In some embodiments, a pressure barrier 210 that is transparent tomicrowave energy can be located within the microwave energy source 204,near the outlet of the microwave energy source, or at other locationsbetween the microwave energy source 204 and the plasma 206 produced inthe FEWG. This pressure barrier 210 can serve as a safety measure toprotect from potential backflow of plasma into the microwave energysource 204. Plasma does not form at the pressure barrier itself;instead, the pressure barrier is simply a mechanical barrier. Someexamples of materials that the pressure barrier can be made of arequartz, ethylene tetrafluoroethylene (ETFE), other plastics, orceramics. In some embodiments, there can be two pressure barriers 210and 211, where one or both pressure barriers 210 and 211 are within themicrowave energy source 204, near the outlet of the microwave energysource, or at other locations between the microwave energy source 204and the plasma 206 produced in the FEWG. In some embodiments, thepressure barrier 211 is closer to the plasma 206 in the FEWG than thepressure barrier 210, and there is a pressure blowout port 212 betweenthe pressure barriers 210 and 211 in case the pressure barrier 211fails.

In some embodiments, the local impedance within the FEWG is tailoredusing filaments, point sources, electrodes and/or magnets. In someembodiments, filaments, point sources, electrodes and/or magnets areused to increase the density plasma within the reaction zone of theFEWG.

FIG. 2B illustrates a microwave processing system with a FEWG andfilaments. In the embodiment of FIG. 2B, the microwave processing system250 includes a microwave energy generator (i.e., a microwave energysource) 254, a FEWG 255, and a microwave emitter circuit 257 similar toprevious embodiments. Microwave energy 259 is supplied by the microwaveenergy source 254, to propagate in a direction down the length L of theFEWG 255. In this embodiment, supply gas inlet 252 is placed near theentrance of the portion L₀, rather than at the entrance to the portionL₁ (i.e., the plasma zone) as was illustrated in previous embodiments.One or more metal filaments 270 is placed within the FEWG 255 to assistin the ignition of the plasma and/or the excitation of higher energyspecies within the plasma. In this embodiment, metal filament 270 isdownstream of the first gas inlet 252, near the entrance to the plasmazone portion of the FEWG L₁ (with a smaller cross-sectional area thanthe FEWG closer to the microwave energy generator). In otherembodiments, the filament 270 may be located at other locations withinportion L₁ of the overall length L of the FEWG 255, where L₁ is theregion in the waveguide where the plasma is formed as described inrelation to previous embodiments. In some embodiments, the filament 270is located within portion L₁ of the FEWG and upstream of the processmaterial inlet 260, so that it will be located outside of the portion L₂(i.e., length L₂ shown in FIG. 2A) where reactions are taking place andwhich could coat the filament with reacted species. The presence offilament 270 can reduce the plasma ignition voltage by providing anignition site, by focusing the electric field of microwave energy 259.Additionally, the filament 270 can become heated and emit electronsthrough thermionic emission, which further contributes to reducing theplasma ignition voltage. Although the filament 270 is illustrated as asingle wire in this embodiment, filament 270 may take otherconfigurations such as a coil or multiple filaments. In someembodiments, the filament 270 is tungsten. In some embodiments, thefilament may be actively energized (powered) or may be passive. In someembodiments, the filament 270 is an osmium filament (e.g., configured asa plate, or coil, or other shape) adjacent to a heater coil. In someembodiments, the filament 270 is a ferrous material in the field of aninductive coil. In some embodiments, the filament 270 is actively heatedwhere the active components (e.g., heating source components) arelocated outside of the waveguide 255 and the filament material that isbeing heated is inside of the waveguide 255.

The filament 270 within the FEWG can assist with the plasma ignition. Insome embodiments, an advantage of using a filament 270 within the FEWGis that it enables a plasma to form quickly enough to keep up with fastmicrowave pulsing frequencies (e.g., at frequencies greater than 500 Hz,or greater than 1 kHz), even with high gas flows (e.g., greater than 5slm) and large gas volumes (e.g., up to 1000 L). This is particularlyimportant at high pressures (e.g., greater than 0.9 atm, or greater than1 atm, or greater than 2 atm), because the high energy species willextinguish quickly in a high pressure atmosphere, and if the plasmacannot ignite fast enough, then there will be a low fraction ofhigh-energy species (i.e., integrated over time) in a pulsed plasma athigh pressures.

In some embodiments, the precursor materials (i.e., process materials)to produce the carbon nanoparticles and the carbon aggregates describedherein are gaseous, including hydrocarbon gases, such as C₂H₂, C₂H₄,C₂H₆, carbon dioxide with water, trimethylaluminum (TMA),trimethylgallium (TMG), glycidyl methacrylate (GMA),methylacetylene-propadiene, propadiene, propane, propyne, acetylene, orany mixture or combination thereof, In some embodiments, the precursorsare other materials used in the semiconductor industry for thedeposition and etching of metals and dielectrics. In some embodiments,the precursor materials (i.e., process materials) to produce the carbonnanoparticles and the carbon aggregates described herein are liquidmixtures, including isopropyl alcohol (IPA), ethanol, methanol,condensed hydrocarbons (e.g., hexane), or other liquid hydrocarbons.

In some embodiments, the carbon nanoparticles and aggregates includingthe different carbon allotropes described herein are produced using themicrowave plasma reactors with gas flows from 1 slm (standard liters perminute) to 1000 slm, or from 2 slm to 1000 slm, or from 5 slm to 1000slm, or greater than 1 slm, or greater than 2 slm, or greater than 5slm, or greater than 10 slm, or greater than 100 slm. In someembodiments, the carbon nanoparticles and aggregates described hereinare produced using the microwave plasma reactors with gas residencetimes from 0.001 seconds to 100 seconds, or from 0.01 seconds to 100seconds, or from 0.1 seconds to 100 seconds, or from 0.001 seconds to 10seconds, or from 0.01 seconds to 10 seconds, or from 0.1 seconds to 10seconds.

In some embodiments, the carbon nanoparticles and aggregates includingthe different carbon allotropes described herein are produced using themicrowave plasma reactors with liquid precursor flows from 0.1 L/min to1000 L/min, or from 2 L/min to 1000 L/min, or from 5 L/min to 1000L/min, or greater than 1 L/min, or greater than 2 L/min, or greater than5 L/min, or greater than 10 L/min, or greater than 100 L/min. In someembodiments, the carbon nanoparticles and aggregates described hereinare produced using the microwave plasma reactors with liquid precursorresidence times from 0.001 seconds to 100 seconds, or from 0.01 secondsto 100 seconds, or from 0.1 seconds to 100 seconds, or from 0.001seconds to 10 seconds, or from 0.01 seconds to 10 seconds, or from 0.1seconds to 10 seconds.

In some embodiments, the precursor material flow rate (i.e., gas orliquid flow rate) is used to tailor the mixture of allotropes producedwithin the reactor. At higher flow rates, the residence times areshorter, and at lower flow rates the residence times are longer. In someembodiments, there is one or more carbon allotropes that form initially,and other carbon allotropes that form subsequently and/or that grow onthe surfaces of the initially formed carbon allotrope. At higher flowrates (i.e., shorter residence times) the ratio of the initially formedallotrope to the subsequently formed allotropes will be higher than itwill be at lower flow rates.

One example is the production of mixtures of graphene, graphite andMWSFs. In some embodiments, MWSFs form first, and the graphene and/orgraphite materials form on the surfaces of the initially formed MWSFs.In embodiments when the mixture is produced with higher flow rates, theratio of graphene and graphite to MWSFs is lower (e.g., as low as 10% or20%). On the other hand, in embodiments when the mixture is producedwith lower flow rates, the ratio of graphene and graphite to MWSFs ishigher (e.g., up to 80% or 90%) because there is more time foradditional layers of graphene and graphite to grow on the MWSF surfaces.

Another example is the production of mixtures of graphene, graphite andamorphous carbon. In some embodiments, amorphous carbon forms first, andthe graphene and/or graphite materials form on the surfaces of theinitially formed amorphous carbon. In embodiments when the mixture isproduced with higher flow rates, the ratio of graphene and graphite toamorphous carbon is lower (e.g., as low as 10% or 20%). On the otherhand, in embodiments when the mixture is produced with lower flow rates,the ratio of graphene and graphite to amorphous carbon is higher (e.g.,up to 80% or 90%) because there is more time for additional layers ofgraphene and graphite to grow on the amorphous carbon surfaces.

It is important to note that other parameters, in addition to precursormaterial flow rate, also affect which carbon allotropes form, and thegrowth rate of each, including, for example, microwave parameters (e.g.,energy, power, pulse rate), chamber geometry, reaction temperature, thepresence of a filament, and the precursor and supply gas speciesutilized. For example, when producing graphene, or mixtures of grapheneand graphite, the microwave energy and power, as well as the precursorand supply gas flow rates can impact the number of layers in thegraphene, and/or the ratio of graphene to graphite produced. At higherpower, the rate of growth of the carbon layers increases, and at longerresidence times the number of layers that are able to grow increases.

In some embodiments, the carbon nanoparticles and aggregates describedherein are produced using the microwave plasma reactors with chambervolumes from 100 cm³ to 100,000 cm³, or from 1000 cm³ to 100,000 cm³, orfrom 100 cm³ to 10,000 cm³, or from 1000 cm³ to 10,000 cm³, or from 1000cm³ to 5,000 cm³. Multiple chambers can also be used in parallel in asingle reactor, and multiple reactors can be used in parallel in thesame reactor system.

In some embodiments, the carbon nanoparticles and aggregates describedherein are produced using the microwave plasma reactors at productionrates greater than 10 kg/hr, or greater than 1 kg/hr, or from 0.1 to 100kg/hr, or from 1 to 100 kg/hr, or from 10 to 100 kg/hr, or from 0.1 to10 kg/hr, or from 0.1 to 1 kg/hr, or from 1 to 10 kg/hr.

A method for generating the carbon particles, nanoparticles, aggregatesand materials described herein produced using microwave plasma reactorsis shown in FIG. 3. In some embodiments, the method 300 comprises 310flowing a process gas into a reaction zone, 320 cracking molecules ofthe process gas in the reaction zone using a microwave plasma, 330reacting the cracked molecules to form carbon aggregates, and 340collecting the carbon aggregates. In some embodiments, the carbonaggregates comprise graphene. In some embodiments, the carbon aggregatescomprise graphene, graphite, MWSFs, connected MWSFs, amorphous carbon,other carbon allotropes, or combinations thereof. In some embodiments,carbon aggregates contain a ratio of carbon to other elements, exceptHydrogen, is greater than 99%, a median size of the carbon aggregates isfrom 1 to 50 microns, a surface area of the carbon aggregates is from 50to 200 m2/g, when measured using the Brunauer-Emmett-Teller (BET) methodwith nitrogen as the adsorbate, and the carbon aggregates, whencompressed, have an electrical conductivity greater than 500 S/m.

Post-Processing Graphite and Graphene Materials

In some embodiments, the carbon particles, nanoparticles and aggregatescontaining graphite and graphene described herein are produced andcollected, and no post-processing is done. In other embodiments, thecarbon particles, nanoparticles and aggregates described herein areproduced and collected, and some post-processing is done. Some examplesof post-processing include mechanical processing, such as ball milling,grinding, attrition milling, micro-fluidizing, jet milling, and othertechniques to reduce the particle size without damaging the carbonallotropes contained within. Some examples of post-processing includeexfoliation processes such as shear mixing, chemical etching, oxidizing(e.g., Hummer method), thermal annealing, doping by adding elementsduring annealing (e.g., S, and N), steaming, filtering, and lypolizing,among others. Some examples of post-processing include sinteringprocesses such as SPS (Spark Plasma Sintering, i.e., Direct CurrentSintering), Microwave, and UV (Ultra-Violet), which can be conducted athigh pressure and temperature in an inert gas. In some embodiments,multiple post-processing methods can be used together or in series. Insome embodiments, the post-processing will produce functionalized carbonnanoparticles or aggregates described herein.

In some embodiments, the materials are mixed together in differentcombinations. In some embodiments, different carbon nanoparticles andaggregates containing graphite and graphene described herein are mixedtogether before post-processing. For example, different carbonnanoparticles and aggregates containing graphite and graphene withdifferent properties (e.g., different sizes, different compositions,different purities, from different processing runs, etc.) can be mixedtogether. In some embodiments, the carbon nanoparticles and aggregatesdescribed herein could be mixed with graphene to change the ratio of thegraphite to graphene in the mixture. In some embodiments, differentcarbon nanoparticles and aggregates containing graphite and graphenedescribed herein are mixed together after post-processing. For example,different carbon nanoparticles and aggregates containing graphite andgraphene with different properties and/or different post-processingmethods (e.g., different sizes, different compositions, differentfunctionality, different surface properties, different surface areas)can be mixed together.

In some embodiments, the carbon nanoparticles and aggregates describedherein are produced and collected, and subsequently processed bymechanical grinding, milling, or exfoliating. In some embodiments, theprocessing (e.g., by mechanical grinding, milling, exfoliating, etc.)reduces the average size of the particles. In some embodiments, theprocessing (e.g., by mechanical grinding, milling, exfoliating, etc.)increases the average surface area of the particles. In someembodiments, the processing by mechanical grinding, milling orexfoliation shears off some fraction of the carbon layers, producingsheets of graphite mixed with the carbon nanoparticles.

In some embodiments, the surface area of the carbon aggregates aftersubsequent processing by mechanical grinding, milling, or exfoliating,when measured using the nitrogen Brunauer-Emmett-Teller (BET) (i.e., theBET method with nitrogen as the adsorbate) or the Density FunctionalTheory (DFT) method, is from 50 to 300 m²/g, or from 100 to 300 m²/g, orfrom 50 to 200 m²/g, or from 50 to 150 m²/g, or from 60 to 110 m²/g, orfrom 50 to 100 m²/g, or from 70 to 100 m²/g.

In some embodiments, the mechanical grinding or milling is performedusing a ball mill, a planetary mill, a rod mill, a shear mixer,high-shear granulator, an autogenous mill, or other type of machine usedto break solid materials into smaller pieces by grinding, crushing orcutting. In some embodiments, the mechanical grinding, milling orexfoliating is performed wet or dry. In some embodiments, the mechanicalgrinding is performed by grinding for some period of time, then idlingfor some period of time, and repeating the grinding and idling for anumber of cycles. The grinding period may be, for example, from 1 minuteto 20 minutes, or from 1 minute to 10 minutes, or from 3 minutes to 8minutes, or approximately 3 minutes, or approximately 8 minutes. In someembodiments, the idling period is from 1 minute to 10 minutes, orapproximately 5 minutes, or approximately 6 minutes. In someembodiments, the number of grinding and idling cycles is from 1 to 100,or from 5 to 100, or from 10 to 100, or from 5 to 10, or from 5 to 20.In some embodiments, the total amount of time grinding and idling isfrom 10 minutes to 1200 minutes, or from 10 minutes to 600 minutes, orfrom 10 minutes to 240 minutes, or from 10 minutes to 120 minutes, orfrom 100 minutes to 90 minutes, or from 10 minutes to 60 minutes, orapproximately 90 minutes, or approximately 120 minutes.

In some embodiments, the grinding steps in the cycle are performed byrotating a mill in one direction for a first cycle (e.g., clockwise),and then rotating a mill in the opposite direction (e.g.,counter-clockwise) for the next cycle. In some embodiments, themechanical grinding or milling is performed using a ball mill, and thegrinding steps are performed using a rotation speed from 100 to 1000rpm, or from 100 to 500 rpm, or approximately 400 rpm. In someembodiments, the mechanical grinding or milling is performed using aball mill using a milling media with a diameter from 0.1 mm to 20 mm, orfrom 0.1 mm to 10 mm, or from 1 mm to 10 mm, or approximately 0.1 mm, orapproximately 1 mm, or approximately 10 mm. In some embodiments, themechanical grinding or milling is performed using a ball mill using amilling media composed of metal such as steel, an oxide such aszirconium oxide (zirconia), yttria stabilized zirconium oxide, silica,alumina, magnesium oxide, or other hard materials such as siliconcarbide or tungsten carbide.

In some embodiments, the carbon nanoparticles and aggregates describedherein are produced and collected, and subsequently processed usingelevated temperatures, such as thermal annealing, or sintering. In someembodiments, the processing using elevated temperatures is done in aninert environment such as nitrogen or argon. In some embodiments, theprocessing using elevated temperatures is done at atmospheric pressure,or under vacuum, or at low pressure. The elevated temperatures may be,for example, temperatures from 500° C. to 2500° C., or from 500° C. to1500° C., or from 800° C. to 1500° C., or from 800° C. to 1200° C., orfrom 800° C. to 1000° C., or from 2000 to 2400° C., or approximately800° C., or approximately 1000° C., or approximately 1500° C., orapproximately 2000° C., or approximately 2400° C.

In some embodiments, the carbon nanoparticles and aggregates describedherein are produced and collected, and subsequently additional elementsor compounds are added, thereby incorporating the unique properties ofthe carbon nanoparticles and aggregates into other mixtures ofmaterials. For example, nickel can be added to increase the magneticpermeability of the carbon nanoparticles and aggregates, or the degreeof magnetization that the carbon nanoparticles and aggregates obtain inresponse to an applied magnetic field. Another example is the additionof sulfur to increase the surface area of the carbon nanoparticles andaggregates by forcing the carbon layers to separate. For example, addingsulfur can increase the surface area by 2 or 3 times compared with thematerial without sulfur. Another method to increase the surface area isthrough oxidation; however, the resulting compounds (e.g., grapheneoxide) are insulators. The methods described herein, e.g., using sulfur,can produce particles with high surface areas that are conductive.

In some embodiments, the surface area of the carbon aggregates aftersubsequent processing that adds sulfur, when measured using the nitrogenBrunauer-Emmett-Teller (BET) or the Density Functional Theory (DFT)method, is from 50 to 300 m²/g, or from 100 to 300 m²/g, or from 50 to200 m²/g, or from 50 to 150 m²/g, or from 60 to 110 m²/g, or from 50 to100 m²/g, or from 70 to 100 m²/g.

In some embodiments, either before or after post-processing, the carbonnanoparticles and aggregates described herein are added to solids,liquids or slurries of other elements or compounds to form additionalmixtures of materials incorporating the unique properties of the carbonnanoparticles and aggregates. In some embodiments, the carbonnanoparticles and aggregates described herein are mixed with other solidparticles, polymers or other materials. The resulting powders orcomposites of the particles in a solid matrix of a different material,can be used in different applications, such as in lubricants orstructural composite materials. In some embodiments, the carbonnanoparticles and aggregates described herein are mixed with liquids toproduce inks for different applications, such as conductive inks. Theresulting inks can also be coated on a substrate or infused in anothermaterial for various applications such as capacitor or batteryelectrodes. In some embodiments, the carbon nanoparticles and aggregatesdescribed herein are mixed with solvents and optionally other particlesto create slurries, which can then be coated or printed onto othersurfaces in various applications, such as printed conductor antennas.

In some embodiments, either before or after post-processing, the carbonnanoparticles and aggregates described herein are used in variousapplications, including but not limited to lubricant formulations (e.g.,lubricants for high-speed or high-stress applications, lubricants forhigh-temperature environments, lubricants for high-thermal conductivityapplications, and anti-stiction lubricants, among others), filtrationand separation applications (e.g., chemical filters, water filtration,desalinization, gas separation, oxidation barrier, impermeablemembranes, non-reactive filters, and carbon sequestration material,among others), transportation and industrial applications (e.g., rubberadditives, tire additives, automobile tire additives, major componentsin tires, functionalized additives for tires, couplings, mounts,elastomeric o-rings, hoses, sealants, and epoxies, among others),metamaterials formulations (e.g., the particles or aggregates decoratedwith Ni, Co or Fe nanowires, carbon dielectric layered materials, andinterface materials with functionalized surfaces, among othercombinations with other materials that result in unexpected properties),electronics ink formulations (e.g., conductive inks, transparentconductive inks, 3D printed circuits and printed circuit boards,resistivity inks, dielectric inks, flexible electronics, piezoelectrics,antennas, rectennas, smart rectennas, electrochromic devices,triboelectric devices, microwave equipment, system inks, andidentification systems, among others), other inks (e.g., cosmetics, and3D printed structural inks, among others), coatings (e.g.,anti-corrosion, super hydrophobic, room heating, de-icing, cooling,electro-static discharge (ESD), radiofrequency shielding (EMF shielding)radiofrequency absorbing (EMF absorbing), and fabric and textilecoatings, among others), capacitor material formulations (e.g., supercapacitor additives, high surface area carbon, high purity carbon, highsurface area high purity carbon, and separators, among others), sensorsand solid state electronics applications (e.g., chemical, humidity,touch, light, transistors, diodes, and integrated devices, amongothers), composite materials formulations (e.g., as additives forcement, steel, aluminum, plastics, and carbon fiber, among others),energy applications (e.g., hydrogen storage, anode composites, cathodecomposites, batteries, fuel cell electrodes, capacitors, andcapacitor/battery hybrids, among others), in-vivo bio-medicalapplications (e.g., tissue engineering, drug delivery, metal delivery,bio-degradable nanowire for neuro regeneration, and better health, amongothers), and ex-vivo bio-medical applications (e.g., filtration, skinelectrodes, and other medical devices).

Additional Embodiments

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including graphene, with no seedparticles. The graphene in the carbon material has up to 15 layers. Aratio of carbon to other elements, except hydrogen, in the carbonaggregates is greater than 99%. A median size of the carbon aggregatesis from 1 to 50 microns. A surface area of the carbon aggregates is atleast 50 m²/g, when measured using a Brunauer-Emmett-Teller (BET) methodwith nitrogen as the adsorbate. The carbon aggregates, when compressed,have an electrical conductivity greater than 500 S/m.

In some embodiments, the carbon material described above also includesone or more other carbon allotropes in addition to graphene, where aratio of the graphene to the other carbon allotropes is greater than90%.

In some embodiments, a Raman spectrum of the carbon material describedabove, using 532 nm incident light, has: a 2D-mode peak, a G-mode peak,and a 2D/G intensity ratio greater than 0.5.

In some embodiments, the surface area of the carbon aggregates describedabove is from 50 to 300 m²/g, when measured using the nitrogen BETmethod.

In some embodiments, the electrical conductivity of the carbonaggregates described above is from 1000 to 20,000 S/m when compressed.

In some embodiments, the carbon material described above furtherincludes amorphous carbon, where a ratio of the amorphous carbon to thegraphene is less than 5%. A Raman spectrum of the carbon materialcomprising the amorphous carbon, using 532 nm incident light, has: a2D-mode peak, a D-mode peak, a G-mode peak, a D/G intensity ratiogreater than 0.5, a low intensity 2D-mode peak, and a shallow valleybetween the D-mode peak and G-mode peak.

In some embodiments, the carbon aggregates described above arepost-processed using a method selected from the group consisting ofmilling, grinding, exfoliating, annealing, sintering, steaming,filtering, lypolizing, doping, and adding elements. For example, thesurface area of the post-processed carbon aggregates may be from 50 to1000 m²/g, when measured using the nitrogen BET method.

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including graphene andmulti-walled spherical fullerenes, with no seed particles. The graphenein the carbon material has up to 15 layers. A Raman spectrum of thecarbon material comprising the multi-walled spherical fullerenes, using532 nm incident light, has: a D-mode peak; a G-mode peak; and a D/Gintensity ratio less than 1.2. A ratio of carbon to other elements,except hydrogen, in the carbon aggregates is greater than 99%. A mediansize of the carbon aggregates is from 1 to 100 microns. A surface areaof the carbon aggregates is at least 10 m²/g, when measured using aBrunauer—Emmett—Teller (BET) method with nitrogen as the adsorbate. Thecarbon aggregates, when compressed, have an electrical conductivitygreater than 500 S/m.

In some embodiments, the Raman spectrum of the carbon material describedabove comprising the multi-walled spherical fullerenes has a D/Gintensity ratio from 0.9 to 1.1.

In some embodiments, a ratio of the multi-walled spherical fullerenes tothe graphene in the carbon material described above is from 20% to 80%.

In some embodiments, the surface area of the carbon aggregates describedabove is from 10 to 200 m²/g, when measured using the nitrogen BETmethod.

In some embodiments, the electrical conductivity of the carbonaggregates described above is from 1000 to 20,000 S/m when compressed.

In some embodiments, the multi-walled spherical fullerenes describedabove include connected multi-walled spherical fullerenes, in which atleast some of the multi-walled spherical fullerenes are coated by layersof the graphene.

In some embodiments, the carbon aggregates described above arepost-processed using a method selected from the group consisting ofmilling, grinding, exfoliating, annealing, sintering, steaming,filtering, lypolizing, doping, and adding elements. The surface area ofthe post-processed carbon aggregates may be, for example, from 50 to 500m²/g, when measured using the BET method with nitrogen as the adsorbate.

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including a mixture of grapheneand at least one other carbon allotrope, with no seed particles. Thegraphene in the carbon material has up to 15 layers. A ratio of carbonto other elements, except hydrogen, in the carbon aggregates is greaterthan 99%. A median size of the carbon aggregates is from 1 to 100microns. A surface area of the carbon aggregates is at least 10 m²/g,when measured using a Brunauer-Emmett-Teller (BET) method with nitrogenas the adsorbate. The carbon aggregates, when compressed, have anelectrical conductivity greater than 100 S/m.

In some embodiments, a ratio of the graphene to the at least one othercarbon allotrope in the carbon material described above is from 5% to95%.

In some embodiments, a Raman spectrum of the carbon material comprisingthe graphene, using 532 nm incident light, has: a 2D-mode peak, a G-modepeak, and a 2D/G intensity ratio greater than 0.5

In some embodiments, the surface area of the carbon aggregates describedabove is from 10 to 200 m²/g, when measured using the BET method withnitrogen as the adsorbate.

In some embodiments, the electrical conductivity of the carbonaggregates described above is from 100 to 20,000 S/m when compressed.

In some embodiments, the at least one other carbon allotrope of thecarbon material described above includes multi-walled sphericalfullerenes. A ratio of the graphene to the multi-walled sphericalfullerenes may be from, for example, 20% to 80%. In certain embodiments,the multi-walled spherical fullerenes include connected multi-walledspherical fullerenes, in which at least some of the multi-walledspherical fullerenes are coated by layers of the graphene.

In some embodiments, the at least one other carbon allotrope describedabove comprises amorphous carbon. A ratio of the graphene to theamorphous carbon may be, for example, greater than 95%.

In some embodiments, the at least one other carbon allotrope in thecarbon material described above comprises predominantly sp³hybridization. For example, the other carbon allotrope in the carbonmaterial described above can comprise a fraction of carbon atoms withsp³ hybridization that is greater than 50%, or greater than 60%, orgreater than 70%, or greater than 80%, or greater than 90%. One methodfor determining the fraction of sp³ hybridization in a carbon allotropeis Raman spectroscopy. In certain embodiments, the ratio of graphene tothe other carbon allotrope having predominantly sp³ hybridization isfrom 5% to 95%.

In some embodiments, the carbon aggregates described above arepost-processed using a method selected from the group consisting ofmilling, grinding, exfoliating, annealing, sintering, steaming,filtering, lypolizing, doping, and adding elements. The surface area ofthe post-processed carbon aggregates may be, for example, from 50 to2000 m²/g, when measured using the BET method with nitrogen as theadsorbate.

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including graphene and amorphouscarbon, with no seed particles. The graphene in the carbon material hasup to 15 layers. A Raman spectrum of the carbon aggregates containingthe amorphous carbon, using 532 nm incident light, has a 2D-mode peak, aD-mode peak and a G-mode peak. A D/G intensity ratio is greater than0.5, with a low intensity 2D-mode peak, and the D-mode peak and G-modepeak have a shallow valley between them. A ratio of carbon to otherelements, except hydrogen, in the carbon aggregates is greater than 99%.A median size of the carbon aggregates is from 1 to 50 microns. Asurface area of the carbon aggregates is greater than 50 m²/g, whenmeasured using the Brunauer—Emmett—Teller (BET) method with nitrogen asthe adsorbate. The carbon aggregates, when compressed, have anelectrical conductivity greater than 500 S/m.

Embodiments of the carbon material described in the preceding paragraphmay include, for example, a ratio of the graphene to amorphous carbonthe carbon material described above is greater than 90%. Embodiments mayalso include, where the surface area of the carbon aggregates describedabove is from 50 to 200 m²/g, when measured using the nitrogen BETmethod. In other embodiments, the electrical conductivity of the carbonaggregates described above is from 1000 to 20,000 S/m when compressed.In further embodiments, the carbon aggregates described above arepost-processed using a method selected from the group consisting ofmilling, grinding, exfoliating, annealing, sintering, steaming,filtering, lypolizing, doping, and adding elements. In yet furtherembodiments, the surface area of the post-processed carbon aggregatesdescribed above is from 50 to 1000 m²/g, when measured using the BETmethod with nitrogen as the adsorbate

In some embodiments, a carbon material comprises a plurality of carbonaggregates, each carbon aggregate having a plurality of carbonnanoparticles, each carbon nanoparticle including amorphous carbon, withno seed particles. A Raman spectrum of the carbon aggregates comprisingamorphous carbon, using 532 nm incident light, has a 2D-mode peak, aD-mode peak and a G-mode peak. A D/G intensity ratio is greater than0.5, with a low intensity 2D-mode peak, and the D-mode peak and G-modepeak have a shallow valley between them. A ratio of carbon to otherelements, except hydrogen, in the carbon aggregates is greater than 99%.A median size of the carbon aggregates is from 1 to 100 microns. Asurface area of the carbon aggregates is greater than 50 m²/g, whenmeasured using the Brunauer—Emmett—Teller (BET) method with nitrogen asthe adsorbate.

Embodiments of the carbon material described in the preceding paragraphmay further include one or more other carbon allotropes in addition tographene, where a ratio of the graphene to the other carbon allotropesis from 5% to 95%. In embodiments of the carbon aggregates describedabove, the surface area is from 50 to 200m²/g, when measured using thenitrogen BET method. In other embodiments, the carbon aggregatesdescribed above are post-processed using a method selected from thegroup consisting of milling, grinding, exfoliating, annealing,sintering, steaming, filtering, lypolizing, doping, and adding elements.In further embodiments, the surface area of the post-processed carbonaggregates described above is from 50 to 2000 m²/g, when measured usingthe BET method with nitrogen as the adsorbate.

In some embodiments, a method for producing carbon aggregates includessupplying microwave energy into a field-enhancing waveguide having areaction zone. A supply gas is added into a supply gas inlet, where thesupply gas inlet is upstream of the reaction zone. A process material isadded into a process material inlet, where the process material flowsinto the reaction zone. The process material is converted into separatedcomponents in the reaction zone. The field-enhancing waveguide may havea field-enhancing zone upstream of the reaction zone. Thefield-enhancing zone may have a decreasing cross-sectional area from afirst cross-sectional area to a second cross-sectional area, where thesecond cross-sectional area extends along a reaction length that formsthe reaction zone of the field-enhancing waveguide. The microwave energypropagates in a direction along the reaction length. A majority of thesupply gas flow is parallel to the direction of the microwave energypropagation in the reaction zone. The supply gas is used to generate aplasma in the plasma zone. The converting of the process material in thereaction zone may occur at a pressure of at least 0.1 atmosphere. Theseparated components include carbon aggregates.

The method described above can be used to produce any of the carbonmaterials described herein. Variations of the method described above canalso be performed to produce any of the carbon materials describedherein.

In some embodiments, a method for producing carbon aggregates includessupplying microwave energy into a field-enhancing waveguide, and addinga supply gas into a supply gas inlet, where the supply gas inlet isupstream of the reaction zone. A process material is added into aprocess material inlet, where the process material flows into thereaction zone. The process material is converted into separatedcomponents in the reaction zone. The field-enhancing waveguide mayinclude a first cross-sectional area and a second cross-sectional area,and a field-enhancing zone between the first cross-sectional area andthe second cross-sectional area. The field-enhancing waveguide may alsoinclude a plasma zone and a reaction zone. The second cross-sectionalarea may be smaller than the first cross-sectional area, where thefield-enhancing zone has a decreasing cross-sectional area from thefirst cross-sectional area to the second cross-sectional area. Thesecond cross-sectional area may be farther away from the microwaveenergy source than the first cross-sectional area, and may extend alonga reaction length that forms the reaction zone of the field-enhancingwaveguide. The microwave energy propagates in a direction along thereaction length. A majority of the supply gas flow is parallel to thedirection of the microwave energy propagation in the reaction zone. Thesupply gas is used to generate a plasma in the plasma zone. Theseparated components include carbon aggregates, where the ratio ofcarbon to other elements, except hydrogen, in the carbon aggregates isgreater than 95% (or greater than 99.5%).

The method described in the preceding paragraph can be used to produceany of the carbon materials described herein. Variations of the methoddescribed above can also be performed to produce any of the carbonmaterials described herein.

In some embodiments, a method for producing carbon aggregates includesflowing a process gas into a reaction zone, and cracking molecules ofthe process gas in the reaction zone using a microwave plasma. Themethod also includes reacting the cracked molecules to form carbonaggregates having a mixture of one or more carbon allotropes, with noseed particle; and collecting the carbon aggregates. A ratio of carbonto other elements, except hydrogen, in the carbon aggregates is greaterthan 99%. A median size of the carbon aggregates is from 1 to 100microns. A surface area of the carbon aggregates is from 50 to 200 m²/g,when measured using the Brunauer—Emmett—Teller (BET) method withnitrogen as the adsorbate. The carbon aggregates, when compressed, havean electrical conductivity greater than 500 S/m. The reaction zone maybe part of a field-enhancing waveguide, where the field-enhancing zonemay have a decreasing cross-sectional area. The one or more carbonallotropes may include graphene, amorphous carbon, MWSFs, and/orconnected MWSFs.

The method described in the above paragraph can be used to produce anyof the carbon materials described herein. Variations of the methoddescribed above can also be performed to produce any of the carbonmaterials described herein.

EXAMPLES

Example 1: Graphite and Graphene Particles Produced Using MicrowavePlasma Reactors

In this first example, carbon particles and aggregates containinggraphite and graphene were generated using a microwave plasma reactorsystem, described in embodiments above. The microwave plasma reactor inthis example had a main body made from stainless steel with a quartzinner wall material. However, the quartz inner wall material is notneeded in all cases, and similar carbon materials can be produced inreactors containing not quartz in or adjacent to the reaction zone. Thereaction zone volume was approximately 45 cm³. The precursor materialwas methane, and was optionally mixed with a supply gas (e.g., argon).The flow rate of methane was from 1 to 20 L/min, the flow rate of thesupply gas was from 0 to 70 L/min. With those flow rates and the toolgeometry, the residence time of the gas in the reaction chamber was fromapproximately 0.001 second to approximately 2.0 seconds, and the carbonparticle production rate was from approximately 0.1 g/hr toapproximately 15 g/hr. After the aggregates were synthesized andcollected, they were post-processed by annealing at a temperature from1000 to 2200° C. in an inert atmosphere for a duration of approximately60 to approximately 600 minutes.

The particles produced in this example contained graphite and graphene,and no seed particles. The particles in this example had a ratio ofcarbon to other elements (other than hydrogen) of approximately 99.97%or greater.

FIG. 4A shows a Raman spectrum of the as-synthesized carbon particles ofthis example, taken using 532 nm incident light. The particles in FIG.4A were produced using precursors containing argon. The spectrum has a2D-mode peak 410 at approximately 2690 cm⁻¹, a G-mode peak 420 atapproximately 1580 cm⁻¹, and a D-mode peak 430 at approximately 1350cm⁻¹, and the 2D/G intensity ratio is greater than 0.5. The 2D/Gintensity ratio for the particles produced in FIG. 4A is approximately0.7.

The size of the aggregates in this example have a median ofapproximately 11.2 microns as-synthesized, and approximately 11.6microns after annealing. The size distribution of the as-synthesizedaggregates had a 10^(th) percentile of approximately 2.7 microns, and a90^(th) percentile of approximately 18.3 microns. The annealedaggregates size distribution had a 10^(th) percentile of approximately4.2 microns, and a 90^(th) percentile of approximately 25.5 microns.

The electrical conductivity of the aggregates was measured after beingcompressed into pellets. The as-synthesized material had a conductivityof 800 S/m when compressed using 2000 psi of pressure, and aconductivity of 1200 S/m when compressed using 12,000 psi of pressure.The annealed material had a conductivity of 1600 S/m when compressedusing 2000 psi of pressure, and a conductivity of 3600 S/m whencompressed using 12,000 psi of pressure.

FIGS. 4B and 4C show SEM images, and FIGS. 4D and 4E show TEM images, ofas-synthesized carbon aggregates of this example showing the graphiteand graphene allotropes. The layered graphene is clearly shown withinthe distortion (wrinkles) of the carbon. The 3D structure of the carbonallotropes is also visible.

The surface area of the aggregates in this example were measured usingthe nitrogen BET method and the DFT method. The surface area of theaggregates as determined by the BET method was approximately 85.9 m²/g.The surface area of the aggregates as determined by the DFT method wasapproximately 93.5 m²/g.

In contrast to conventionally produced carbon materials, the microwaveplasma reactor produced carbon particles and aggregates in this examplecontained graphite and graphene and no seed particles, and had highpurity, Raman signatures indicating a high degree of order, highelectrical conductivities, and large surface areas.

Example 2: Graphite, Graphene and Multi-Walled Spherical FullereneParticles Produced Using Microwave Plasma Reactors

In this second example, carbon particles and aggregates containinggraphite, graphene, MWSFs, and connected MWSFs were generated using amicrowave plasma reactor system described in Example 1, with theaddition of a filament that includes a tantalum/tungsten resistive wire.The precursor material was methane, and was optionally mixed with asupply gas (e.g., argon). The flow rate of methane was from 1 to 100L/min, and the flow rate of the supply gas was from 0 to 100 L/min. Withthose flow rates and the tool geometry, the residence time of the gas inthe reaction chamber was from approximately 0.001 second toapproximately 2.0 seconds, and the carbon particle production rate wasfrom approximately 0.1 g/hr to approximately 15 g/hr. After theaggregates were synthesized and collected, they were post-processed byannealing at a temperature from 1000 to 2200° C. in an inert atmospherefor a duration of approximately 60 to approximately 600 minutes.

The particles produced in this example contained graphite, graphene,MWSFs and no seed particles. The particles in this example had a ratioof carbon to other elements (other than hydrogen) of approximately 99.5%or greater.

FIGS. 5A-5D show Raman spectra of the as-synthesized carbon particles ofthis example, taken using 532 nm incident light. FIGS. 5A and 5C are topdown microscope images of the same region of a sample. The circles inFIG. 5A are regions where the Raman spectra indicate MWSF and connectedMWSF materials are present. FIG. 5B is an example of a Raman spectrafrom one of the circled regions in FIG. 5A. The Raman spectra in FIG. 5Bhas a G-mode peak 510 at approximately 1580 cm⁻¹, and a D-mode peak 520at approximately 1350 cm⁻¹, and the D/G intensity ratio is approximately0.9. The circles in FIG. 5C are regions where the Raman spectra indicategraphite and graphene materials are present. FIG. 5D is an example of aRaman spectra from one of the circled regions in FIG. 5C. The Ramanspectra in FIG. 5D has a 2D-mode peak 530 at approximately 2690 cm⁻¹, aG-mode peak 540 at approximately 1580 cm⁻¹, and a D-mode peak 550 atapproximately 1350 cm⁻¹, and the 2D/G intensity ratio is approximately0.6.

The size of the aggregates in this example have a median fromapproximately 10.2 microns to 19.0 microns as-synthesized, and the sizeremained approximately the same after annealing. The particle sizedistribution of the as-synthesized aggregates had a 10^(th) percentilefrom approximately 1.8 microns to approximately 6.5 microns, and a90^(th) percentile from approximately 18.0 microns to approximately 37.3microns. The particle size distribution of the annealed aggregatesremained approximately the same after annealing.

The electrical conductivity of the aggregates was measured after beingcompressed into pellets. The as-synthesized material had a conductivityof 2100 S/m when compressed using 2000 psi of pressure, and aconductivity of 4300 S/m when compressed using 12,000 psi of pressure.The annealed material had a conductivity of 2300 S/m when compressedusing 2000 psi of pressure, and a conductivity of 4100 S/m whencompressed using 12,000 psi of pressure.

FIGS. 5E-5J show TEM images of as-synthesized carbon aggregates of thisexample showing graphite, graphene and MWSF allotropes. The images inFIGS. 5E-5G mainly show graphite and graphene materials, and the imagesin FIGS. 5H-5J show the MWSFs present in the material. The images showcarbon nanoparticles containing the MWSFs, and connected MWSFs, withlayers of graphene coating and connecting the MWSFs.

The surface area of the aggregates in this example were measured usingthe nitrogen BET method and the DFT method. The surface area of theaggregates as determined by the BET method was from approximately 69.8m²/g to approximately 106.7 m²/g. The surface area of the aggregates asdetermined by the DFT method was from approximately 67.3.5 m²/g toapproximately 106.4 m²/g.

In contrast to conventionally produced carbon materials, the microwaveplasma reactor produced carbon particles and aggregates in this examplecontained graphite, graphene, MWSFs and no seed particles, and had highpurity, Raman signatures indicating a high degree of order, highelectrical conductivities, and large surface areas.

Example 3: Graphite, Graphene and Amorphous Carbon Particles ProducedUsing Microwave Plasma Reactors

In this third example, carbon particles and aggregates containinggraphite, graphene and amorphous carbon were generated using a microwaveplasma reactor system as described in Example 1. The precursor materialcontained methane, or isopropyl alcohol (IPA), or ethanol, or acondensed hydrocarbon (e.g., hexane). The carbon containing precursorswere optionally mixed with a supply gas (e.g., argon). When gaseousmethane was used, the flow rate of methane was from 1 to 20 L/min, andthe flow rate of the supply gas was from 0 to 70 L/min. When theprecursor material was a liquid mixture of IPA and ethanol, the flowrate of the liquid mixture was from 0.1 to 100 mL/min. In some othercases, a condensed hydrocarbon was used and the flow rate of thehydrocarbon was approximately 3 L/min. With those flow rates and thetool geometry, the residence time of the gas in the reaction chamber wasfrom approximately 0.001 second to approximately 2.0 seconds, and thecarbon particle production rate was from approximately 0.1 g/hr toapproximately 15 g/hr. After the aggregates were synthesized andcollected, they were post-processed by annealing at a temperature from1000 to 2200° C. in an inert atmosphere for a duration of approximately60 to approximately 600 minutes.

The particles produced in this example contained graphite, graphene,amorphous carbon and no seed particles. The particles in this examplehad a ratio of carbon to other elements (other than hydrogen) ofapproximately 99.5% or greater.

FIGS. 6A and 6B show Raman spectra of the as-synthesized carbonparticles of this example, taken using 532 nm incident light. FIG. 6Ashows a Raman spectra indicative of the amorphous carbon allotropepresent in the material. The spectra in FIG. 6A has a 2D-mode peak 610at approximately 2690 cm⁻¹, a G-mode peak 620 at approximately 1580cm⁻¹, and a D-mode peak 630 at approximately 1350 cm⁻¹, the D/Gintensity ratio is approximately 0.9, there is low intensity 2D-modepeak, and the D-mode peak and G-mode peak have a shallow valley betweenthem. FIG. 6B shows a Raman spectra indicative of the graphite andgraphene allotropes present in the material. The Raman spectra in FIG.6B has a 2D-mode peak at approximately 2690 cm⁻¹, a G-mode peak atapproximately 1580 cm⁻¹, and a D-mode peak at approximately 1350 cm⁻¹,and the 2D/G intensity ratio is approximately 0.6.

The size of the aggregates in this example have a median fromapproximately 12.5 microns to 18.7 microns as-synthesized. The particlesize distribution of the as-synthesized aggregates had a 10^(th)percentile from approximately 2.4 microns to approximately 5.0 microns,and a 90^(th) percentile from approximately 19.5 microns toapproximately 30.4 microns.

The electrical conductivity of the aggregates was measured after beingcompressed into pellets. The as-synthesized material had a conductivityof approximately 1300 S/m when compressed using 2000 psi of pressure,and a conductivity of approximately 2200 S/m when compressed using12,000 psi of pressure.

FIGS. 6C-6E show TEM images of as-synthesized carbon nanoparticles ofthis example showing the graphite, graphene and amorphous carbonallotropes. The layers of graphene and other carbon materials can beclearly seen in the images.

The surface area of the aggregates in this example were measured usingthe nitrogen BET method and the DFT method. The surface area of theaggregates as determined by the BET method was approximately 74.9 m²/g.The surface area of the aggregates as determined by the DFT method wasapproximately 76.5 m²/g.

In contrast to conventionally produced carbon materials, the microwaveplasma reactor produced carbon particles and aggregates in this examplecontained graphite, graphene and amorphous carbon allotropes and no seedparticles, and had high purity, Raman signatures indicating a highdegree of order, high electrical conductivities, and large surfaceareas.

Reference has been made in detail to embodiments of the disclosedinvention, one or more examples of which have been illustrated in theaccompanying figures. Each example has been provided by way ofexplanation of the present technology, not as a limitation of thepresent technology. In fact, while the specification has been describedin detail with respect to specific embodiments of the invention, it willbe appreciated that those skilled in the art, upon attaining anunderstanding of the foregoing, may readily conceive of alterations to,variations of, and equivalents to these embodiments. For instance,features illustrated or described as part of one embodiment may be usedwith another embodiment to yield a still further embodiment. Thus, it isintended that the present subject matter covers all such modificationsand variations within the scope of the appended claims and theirequivalents. These and other modifications and variations to the presentinvention may be practiced by those of ordinary skill in the art,without departing from the scope of the present invention, which is moreparticularly set forth in the appended claims. Furthermore, those ofordinary skill in the art will appreciate that the foregoing descriptionis by way of example only, and is not intended to limit the invention.

What is claimed is:
 1. A carbon material comprising: a plurality ofcarbon aggregates, each carbon aggregate comprising a plurality ofcarbon nanoparticles, each carbon nanoparticle comprising graphene, withno seed particles; wherein: the graphene in the plurality of carbonnanoparticles comprises up to 15 layers; a percentage of carbon to otherelements, except hydrogen, in the carbon aggregates is greater than 99%;a median size of the carbon aggregates that comprise the carbonnanoparticles is from 1 to 50 microns; a surface area of the carbonaggregates is from 50 m²/g to 300 m²/g, when measured via aBrunauer-Emmett-Teller (BET) method with nitrogen as the adsorbate; andthe carbon aggregates, when compressed, have an electrical conductivityfrom 500 S/m to 20,000 S/m.
 2. The carbon material of claim 1, furthercomprising one or more other carbon allotropes in addition to graphene,wherein a percentage of the graphene to the other carbon allotropes isgreater than 90%.
 3. The carbon material of claim 1, wherein a Ramanspectrum of the carbon material, using 532 nm incident light, comprises:a 2D-mode peak; a G-mode peak; and a 2D/G intensity ratio greater than0.5.
 4. The carbon material of claim 1, further comprising amorphouscarbon, wherein: a percentage of the amorphous carbon to the graphene isless than 5%; and a Raman spectrum of the carbon material comprising theamorphous carbon, using 532 nm incident light, comprises: a 2D-modepeak; a D-mode peak; a G-mode peak; a D/G intensity ratio greater than0.5; a low intensity 2D-mode peak; and a shallow valley between theD-mode peak and G-mode peak.
 5. The carbon material of claim 1, whereinthe carbon aggregates are post-processed using a method selected fromthe group consisting of milling, grinding, exfoliating, annealing,sintering, steaming, filtering, lypolizing, doping, and adding elements.6. The carbon material of claim 5, wherein the surface area of thepost-processed carbon aggregates is from 50 to 1000 m²/g, when measuredusing the BET method with nitrogen as the adsorbate.
 7. A carbonmaterial comprising: a plurality of carbon aggregates, each carbonaggregate comprising a plurality of carbon nanoparticles, each carbonnanoparticle comprising graphene and multi-walled spherical fullerenes,with no seed particles; wherein: the graphene in the plurality of carbonnanoparticles comprises up to 15 layers; a Raman spectrum of the carbonmaterial comprising the multi-walled spherical fullerenes, using 532 nmincident light, comprises: a D-mode peak; a G-mode peak; and a D/Gintensity ratio less than 1.2; a percentage of carbon to other elements,except hydrogen, in the carbon aggregates is greater than 99%; a mediansize of the carbon aggregates that comprise the carbon nanoparticles isfrom 1 to 100 microns; a surface area of the carbon aggregates is atleast from 10 m²/g to 300 m²/g, when measured using aBrunauer-Emmett-Teller (BET) method with nitrogen as the adsorbate; andthe carbon aggregates, when compressed, have an electrical conductivityfrom 500 S/m to 20,000 S/m.
 8. The carbon material of claim 7, whereinthe D/G intensity ratio is from 0.9 to 1.1.
 9. The carbon material ofclaim 7, wherein a ratio percentage of the multi-walled sphericalfullerenes to the graphene is from 20% to 80%.
 10. The carbon materialof claim 7, wherein the multi-walled spherical fullerenes compriseconnected multi-walled spherical fullerenes, in which at least some ofthe multi-walled spherical fullerenes are coated by layers of thegraphene.
 11. The carbon material of claim 7, wherein the carbonaggregates are post-processed using a method selected from the groupconsisting of milling, grinding, exfoliating, annealing, sintering,steaming, filtering, lypolizing, doping, and adding elements.
 12. Thecarbon material of claim 11, wherein the surface area of thepost-processed carbon aggregates is from 50 to 500 m²/g, when measuredusing the BET method with nitrogen as the adsorbate.
 13. A carbonmaterial comprising: a plurality of carbon aggregates, each carbonaggregate comprising a plurality of carbon nanoparticles, each carbonnanoparticle comprising a mixture of graphene and at least one othercarbon allotrope, with no seed particles; wherein: the graphene in theplurality of carbon nanoparticles comprises up to 15 layers; apercentage of carbon to other elements, except hydrogen, in the carbonaggregates is greater than 99%; a median size of the carbon aggregatesthat comprise the carbon nanoparticles is from 1 to 100 microns; asurface area of the carbon aggregates is from 10 m²/g to 300 m²/g, whenmeasured using a Brunauer-Emmett-Teller (BET) method with nitrogen asthe adsorbate; and the carbon aggregates, when compressed, have anelectrical conductivity from 100 S/m to 20,000 S/m.
 14. The carbonmaterial of claim 13, wherein a percentage of the graphene to the atleast one other carbon allotrope is from 5% to 95%.
 15. The carbonmaterial of claim 13, wherein a Raman spectrum of the carbon materialcomprising the graphene, using 532 nm incident light, comprises: a2D-mode peak; a G-mode peak; and a 2D/G intensity ratio greater than0.5.
 16. The carbon material of claim 13, wherein the at least one othercarbon allotrope comprises multi-walled spherical fullerenes.
 17. Thecarbon material of claim 16, wherein a percentage of the graphene to themulti-walled spherical fullerenes is from 20% to 80%.
 18. The carbonmaterial of claim 16, wherein the multi-walled spherical fullerenescomprise connected multi-walled spherical fullerenes, in which at leastsome of the multi-walled spherical fullerenes are coated by layers ofthe graphene.
 19. The carbon material of claim 13, wherein the at leastone other carbon allotrope comprises amorphous carbon.
 20. The carbonmaterial of claim 19, wherein a percentage of the graphene to theamorphous carbon is greater than 95%.
 21. The carbon material of claim13, wherein the at least one other carbon allotrope comprisespredominantly sp³ hybridization.
 22. The carbon material of claim 21,wherein the percentage of graphene to the at least one other carbonallotrope is from 5% to 95%.
 23. The carbon material of claim 13,wherein the carbon aggregates are post-processed using a method selectedfrom the group consisting of milling, grinding, exfoliating, annealing,sintering, steaming, filtering, lypolizing, doping, and adding elements.24. The carbon material of claim 23, wherein the surface area of thepost-processed carbon aggregates is from 50 to 2000 m²/g, when measuredusing the BET method with nitrogen as the adsorbate.